The effect of target-gas purity on the chemical form of F-18 during 18F-F2 production using the neon/fluorine target.

Irradiation of gas mixtures of F2/Ne (20Ne leads to d,alpha 18F) which contained percent levels ( > 0.1%) of N2, CO2, CO2, or CF4 resulted in the production of unacceptable levels of F-18-labeled NF3 and CF4 at the expense of 18F-F2. Analycical gas chromatographic methods have been devised to determine contaminant levels in the target gas as well as in the products arising from them. Commercial mixtures of 1T F2/Ne, pur F2, and neon have been analyzed for contaminants (N2, O2, CO, CO2, and CF4) and found to vary widely in the levels of these impurities from batch to batch. The N2 levels in the 1% F2/Ne mixtures varied from 0.039 to 0.49%, and the CO2 levels from 0o.018 to 0.13%. No detectable impurities were found in the neon (Research Purity), but F2 was found to contain approximately 11% CF4. Reproducibly high yields of 18F-F2 are obtained if the levels of N2, CO2, and CF4 in the final target gas mixture are < 0.01% and carrier F2 is approximately 0.1%. Hydrocarbons and CO were not detected in our gas mixtures, but would also be expected to decrease yields of 18F-F2.